
/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_chebyshev_distance_f32.c
 * Description:  Chebyshev distance between two vectors
 *
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"
#include <limits.h>
#include <math.h>


/**
  @addtogroup FloatDist
  @{
 */


/**
 * @brief        Chebyshev distance between two vectors
 * @param[in]    pA         First vector
 * @param[in]    pB         Second vector
 * @param[in]    blockSize  vector length
 * @return distance
 *
 */

#if defined(ARM_MATH_MVEF) && !defined(ARM_MATH_AUTOVECTORIZE)

#include "arm_helium_utils.h"
#include "arm_vec_math.h"

float32_t arm_chebyshev_distance_f32(const float32_t *pA, const float32_t *pB, uint32_t blockSize)
{
	uint32_t        blkCnt;     /* loop counters */
	f32x4_t         vecA, vecB;
	f32x4_t         vecDiff = vdupq_n_f32(0.0);
	float32_t       maxValue = 0.0;


	blkCnt = blockSize >> 2;
	while (blkCnt > 0U) {
		vecA = vld1q(pA);
		pA += 4;
		vecB = vld1q(pB);
		pB += 4;
		/*
		 * update per-lane max.
		 */
		vecDiff = vmaxnmaq(vsubq(vecA, vecB), vecDiff);
		/*
		 * Decrement the blockSize loop counter
		 */
		blkCnt--;
	}
	/*
	 * tail
	 * (will be merged thru tail predication)
	 */
	blkCnt = blockSize & 3;
	if (blkCnt > 0U) {
		mve_pred16_t    p0 = vctp32q(blkCnt);

		vecA = vldrwq_z_f32(pA, p0);
		vecB = vldrwq_z_f32(pB, p0);

		/*
		 * Get current max per lane and current index per lane
		 * when a max is selected
		 */
		vecDiff = vmaxnmaq_m(vecDiff, vsubq(vecA, vecB), p0);
	}
	/*
	 * Get max value across the vector
	 */
	return vmaxnmavq(maxValue, vecDiff);
}

#else
#if defined(ARM_MATH_NEON)

#include "NEMath.h"

float32_t arm_chebyshev_distance_f32(const float32_t *pA, const float32_t *pB, uint32_t blockSize)
{
	float32_t diff = 0.0f, maxVal = 0.0f, tmpA, tmpB;
	uint32_t blkCnt;
	float32x4_t a, b, diffV, maxValV;
	float32x2_t maxValV2;

	if (blockSize <= 3) {
		tmpA = *pA++;
		tmpB = *pB++;
		diff = fabsf(tmpA - tmpB);
		maxVal = diff;
		blockSize--;

		while (blockSize > 0) {
			tmpA = *pA++;
			tmpB = *pB++;
			diff = fabsf(tmpA - tmpB);
			if (diff > maxVal) {
				maxVal = diff;
			}
			blockSize --;
		}
	} else {

		a = vld1q_f32(pA);
		b = vld1q_f32(pB);
		pA += 4;
		pB += 4;

		diffV = vabdq_f32(a, b);

		blockSize -= 4;

		maxValV = diffV;


		blkCnt = blockSize >> 2;
		while (blkCnt > 0) {
			a = vld1q_f32(pA);
			b = vld1q_f32(pB);

			diffV = vabdq_f32(a, b);
			maxValV = vmaxq_f32(maxValV, diffV);

			pA += 4;
			pB += 4;
			blkCnt --;
		}
		maxValV2 = vpmax_f32(vget_low_f32(maxValV), vget_high_f32(maxValV));
		maxValV2 = vpmax_f32(maxValV2, maxValV2);
		maxVal = vget_lane_f32(maxValV2, 0);


		blkCnt = blockSize & 3;
		while (blkCnt > 0) {
			tmpA = *pA++;
			tmpB = *pB++;
			diff = fabsf(tmpA - tmpB);
			if (diff > maxVal) {
				maxVal = diff;
			}
			blkCnt --;
		}
	}
	return (maxVal);
}

#else
float32_t arm_chebyshev_distance_f32(const float32_t *pA, const float32_t *pB, uint32_t blockSize)
{
	float32_t diff = 0.0f,  maxVal, tmpA, tmpB;

	tmpA = *pA++;
	tmpB = *pB++;
	diff = fabsf(tmpA - tmpB);
	maxVal = diff;
	blockSize--;

	while (blockSize > 0) {
		tmpA = *pA++;
		tmpB = *pB++;
		diff = fabsf(tmpA - tmpB);
		if (diff > maxVal) {
			maxVal = diff;
		}
		blockSize --;
	}

	return (maxVal);
}
#endif
#endif /* defined(ARM_MATH_MVEF) && !defined(ARM_MATH_AUTOVECTORIZE) */


/**
 * @} end of FloatDist group
 */
